G-Clamp Heterocycle Modification Containing Interstrand Photo-Cross-Linker to Capture Intracellular MicroRNA Targets.

MicroRNAs (miRNAs) play indispensable roles in post-transcriptional gene regulation. The identification of target mRNAs is essential for dissecting the recognition basis, dynamics, and regulatory mechanism of miRNA-mRNA interactions. However, the lack of an unbiased method for detecting weak miRNA-mRNA interactions remains a long-standing obstacle for miRNA research. Here, we develop and provide proof-of-concept evidence demonstrating a chemical G-clamp-enhanced photo-cross-linking strategy for covalent capture of intracellular miRNA targets in different cell lines. This approach relies on an aryl-diazirine-G-clamp-modified-nucleoside (ARAGON) miRNA probe containing an alkynyl group that improves the thermal stability of miRNA-target mRNA duplex molecules and can rapidly cross-link with the complementary strand upon UV 365 nm activation, enhancing the transient capture of mRNA targets. After validating the accuracy and binding properties of ARAGON-based miRNA probes through the successful enrichment for the known targets of miR-106a, miR-21, and miR-101, we then extend ARAGON's application to screen for previously unknown targets of different miRNAs in various cell lines. Ultimately, results in this study uncover GAB1 as a target of miR-101 in H1299 lung cancer cells and show that miR-101 silencing of GAB1 can promote apoptosis in H1299 cells, suggesting an oncogenic mechanism of GAB1. This study thus provides a powerful and versatile tool for enhanced screening of global miRNA targets in cells to facilitate investigations of miRNA functions in fundamental cellular processes and disease pathogenesis.